Constructive arrangement for a resonant compressor

ABSTRACT

A constructive arrangement for a resonant compressor comprising a shell ( 1 ), within which are mounted: a non-resonant assembly formed by a motor and a cylinder ( 2 ), said motor having a coil ( 6 ) generating a magnetic flow that travels through the shell ( 1 ); a resonant assembly formed by a piston ( 10 ) reciprocating inside the cylinder ( 2 ) and by an actuating means ( 3 ) operatively coupling the piston ( 10 ) to the motor, said arrangement comprising a magnetic insulating means, which is affixed to one of the parts defined by the shell ( 1 ), by the resonant assembly, and by the non-resonant assembly, and which is arranged so as to interrupt the magnetic flow path between the shell ( 1 ) and at least one of the parts defined by the piston ( 10 ) and the cylinder ( 2 ) in a direction substantially parallel to the displacement direction of the piston ( 10 ).

FIELD OF THE INVENTION

The present invention refers, generally, to a constructive arrangementfor a resonant compressor of the type driven by a linear motor, to beapplied to refrigeration systems and presenting a piston reciprocatinginside a cylinder.

BACKGROUND OF THE INVENTION

In a reciprocating compressor driven by a linear motor, the gas suctionand gas compression operations are performed by the reciprocating axialmovements of each piston inside a cylinder, which is closed by acylinder head and mounted within a hermetic shell, in the cylinder headbeing positioned the suction and discharge valves that control theadmission and discharge of the gas in relation to the cylinder. Thepiston is driven by an actuating means that supports magnetic componentsoperatively associated with a linear motor affixed to the shell of thecompressor. In some known constructions, each piston-actuating meansassembly is connected to a resonant spring affixed to the hermetic shellof the compressor, in order to operate as a guide for the axialdisplacement of the piston and make the whole assembly to act resonantlyin a predetermined frequency, allowing the linear motor to be adequatelydimensioned to continuously supply energy to the compressor uponoperation.

In a known construction for a linear compressor, the linear motor ismounted around the cylinder and the piston and comprises a stack ofinternal laminations with a coil inserted therein, and a stack ofexternal laminations, the magnetic actuator being linearly displacedthrough the space formed by these two stacks of laminations.

The magnetic flow generated by the passage of an alternating currentthrough the coil travels through the structure of the linear motor,supplying the necessary power for the axial displacement of the magnet,which is rigidly connected to the linear motor.

However, part of the magnetic flow generated by the coil also travelsthrough other components of the linear compressor, such as the pistonand the cylinder, which are both generally made of cast iron, closing amagnetic circuit with the shell of the compressor. This magnetic circuitcauses the generation of Foucault currents in these components,generating electric losses in the compressor.

According to the known prior art, in order to avoid such losses, atleast part of the components through which is established the Foucaultcurrent should be manufactured in non-magnetic materials, such asaluminum, in order to interrupt a significant amount of the peripheralflow that is generated. However, producing components with suchmaterials, which are very expensive, sometimes makes economicallyimpractical the manufacture of the compressor.

OBJECT OF THE INVENTION

Thus, it is an object of the present invention to provide a constructivearrangement for a resonant compressor, which without causing energeticlosses during the movement of the piston, minimizes the presence ofFoucault currents in a closed circuit with the components of thecompressor.

A further object is to provide an arrangement such as mentioned above,which minimizes the presence of Foucault currents, without increasingthe cost of the compressor and making impractical its manufacture.

SUMMARY OF THE INVENTION

These and other objects are attained through a constructive arrangementfor a resonant compressor comprising a shell, within which are mounted:a non-resonant assembly formed by a motor and a cylinder, said motorhaving a coil generating a magnetic flow that travels through the shell;a resonant assembly formed by a piston reciprocating inside thecylinder, and by an actuating means operatively coupling the piston tothe motor, said arrangement comprising a magnetic insulating means,which is affixed to one of the parts defined by the shell, the resonantassembly, and the non-resonant assembly, and which is arranged tointerrupt the magnetic flow path between the shell and at least one ofthe parts defined by the piston and by the cylinder in a directionsubstantially parallel to the displacement direction of the piston.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described below, with reference to the encloseddrawings, in which:

FIG. 1 is a schematic longitudinal diametrical sectional view of ahermetic compressor of the type driven by a linear motor constructedaccording to the prior art;

FIG. 2 is a schematic partial longitudinal diametrical sectional view ofthe hermetic compressor illustrated in FIG. 1, presenting some magneticflow lines traveling through the shell of the compressor and part of thecomponents thereof, such as the piston and the cylinder; and

FIG. 3 is a schematic view, such as that of FIG. 2, presenting somemagnetic flow lines traveling through the shell and through part of thecomponents of the compressor, according to the arrangement of thepresent invention.

DESCRIPTION OF THE ILLUSTRATED EMBODIMENT

The present invention will be described in relation to a reciprocatingcompressor driven by a linear motor of the type utilized inrefrigeration systems and comprising a hermetic shell 1, within which ismounted a motor-compressor assembly including a non-resonant assemblyaffixed to the inside of said shell 1 and formed by a linear motor and acylinder 2, and a resonant assembly formed by a piston 10 reciprocatinginside the cylinder 2 and by an actuating means 3 external to thecylinder 2 and which carries a magnet 4 to be axially impelled uponenergization of the linear motor, said actuating means 3 operativelycoupling the piston 10 to the linear motor.

As illustrated in the enclosed drawings, the linear motor is mountedaround the cylinder 2 and the piston 10 and comprises a stack ofinternal laminations 5 with a coil 6 inserted therein, and a stack ofexternal laminations 7. The energization of the coil 6 by thealternating current passing therethrough generates a magnetic flow thattravels through the structure of the motor, allowing the movement ofboth the magnet 4 and the piston 10.

According to the illustration in FIG. 2, in the prior art construction,the magnetic flow generated by the coil 6 travels through the structureof the linear motor, as well as through the shell 1 and other componentsof the compressor, closing circuits of magnetic flow lines which allowFoucault currents to be generated in these components, generatingelectric losses to the compressor.

In this construction, the piston 10 and the cylinder 2 are manufacturedin a magnetic material, for example cast iron.

In the illustrated construction, the compressor also includes springmeans 8, for example in the form of helical springs, mounted underconstant compression to the resonant assembly and to the non-resonantassembly and which are resiliently and axially deformable in thedisplacement direction of the piston 10.

In the embodiment illustrated in FIG. 1, the cylinder 2 has an endclosed by a valve plate 20 provided with a suction valve and a dischargevalve, which are not illustrated, allowing the selective fluidcommunication between a compression chamber 9 that is defined between atop portion 11 of the piston 10 and the valve plate 20, and respectiveinternal portions of a cylinder head 30 that are respectively maintainedin fluid communication with the low and high pressure sides of therefrigeration system to which the compressor is coupled. In thisconstruction, the valve plate 20 is generally made of a ferrousmaterial, such as cast or sintered iron, and the cylinder head 30 isgenerally made of a non-magnetic material, such as aluminum, forming abarrier to the path of the magnetic flow lines through said component.

The present invention provides a constructive arrangement for theresonant compressor of the type described above and comprising amagnetic insulating means, which is affixed to one of the parts definedby the shell 1, by the resonant assembly, and by the non-resonantassembly, and which is arranged to interrupt the magnetic flow pathbetween the shell 1 and at least one of the parts defined by the piston10 and by the cylinder 2, in a direction substantially parallel to thedisplacement direction of the piston 10.

Although only one specific construction for the present invention, to bedescribed below, has been illustrated, it should be understood that theinvention also comprises other constructive options, such as that inwhich the magnetic insulating means interrupts the magnetic flow pathbetween the non-resonant assembly and at least one of said parts definedby the piston 10 and the cylinder 2, for example, particularlyinterrupting the magnetic flow path between the spring means 8 disposedbetween the non-resonant assembly and the actuating means 3 and thelatter, and more particularly between said non-resonant assembly and atleast the piston 10.

The present solution also foresees a constructive option, in which amagnetic insulating means is disposed to interrupt the magnetic flowbetween the actuating means 3 and at least said piston 10. Since theFoucault currents generate more losses when the magnetic flow lines arecrossing bodies of higher mass, the present invention, when appliedbetween the actuating means 3 and the piston 10 and the cylinder 2,provides a magnetic insulating means preferably between said actuatingmeans and the piston 10, as described hereafter, and it can additionallyprovide the magnetic insulating means between the actuating means 3 andthe cylinder 2.

In this constructive option, the magnetic insulating means is defined byat least part of the piston 10, and it can also be defined by at leastpart of the cylinder 2.

While the solution in which the whole piston 10 is constructed in amagnetic insulating material interrupts the magnetic flow traversingthese components of the compressor, such solution, besides beingexpensive is not the ideal one because the piston 10 does not form anadequate tribologic pair with the cylinder 2. On the other hand, theconstruction of the cylinder 2 in a magnetic insulating material that istribologically compatible with the piston 10, not only makes theconstruction of the compressor impractical, as a function of the highcost thereof, but also results in an insatisfactory tribologic pair,which is not the more adequate one when cast iron is used.

In a constructive option of the present solution, the magneticinsulating means comprises, for example at least one element made of anon-magnetic material disposed between the piston 10 and the actuatingmeans 3, and each element in a non-magnetic material can be defined by acoupling portion 12 of the piston 10 connecting the actuating means 3 tothe top portion 11 of the piston 10. In this construction, said topportion 11 is made of a magnetic material tribologically compatible withthat of the cylinder 2, such as cast iron. In a variation of saidconstructive option, in which, for example, the piston 10 is massive,each element of a non-magnetic material is in the form of a pastille,not illustrated, defined adjacent to the actuating means 3 andattachable to a respective part defined by the piston 10, and which canalso be attached to the cylinder 2.

In another constructive option, the coupling portion 12 defines themagnetic insulating means and is mounted to the piston 10 through arespective end mounted to the top portion 11 of the piston 10, forexample affixed to the inside of said top portion 11 when the latter istubular.

In the illustrated construction, the coupling portion 12 is an insertmade of a non-magnetic material, such as aluminum and, for example 10 mmthick, which is mounted to the inside of the top portion 11 of thepiston 10 made of a material tribologically compatible with that of thecylinder 2. The fixation between the coupling portion 12 and the topportion 11 of the piston 10 can be made by any one of the processes,such as interference, welding, and gluing.

Although not illustrated, the interruption of the magnetic flow in thepresent invention can be achieved through a magnetic insulating means inthe form of a lining provided in the part to which it is affixed.

1. A constructive arrangement for a resonant compressor comprising a shell (1), within which are mounted: a non-resonant assembly formed by a motor and a cylinder (2), said motor having a coil (6) generating a magnetic flow which travels through the shell (1); a resonant assembly formed by a piston (10) reciprocating inside the cylinder (2) and by an actuating means (3) operatively coupling the piston (10) to the motor, characterized in that it comprises a magnetic insulating means, which is affixed to one of the parts defined by the shell (1), by the resonant assembly, and by the non-resonant assembly, and which is arranged to interrupt the magnetic flow path between the shell (1) and at least one of the parts defined by the piston (10) and by the cylinder (2) in a direction substantially parallel to the displacement direction of the piston (10).
 2. The arrangement according to claim 1, characterized in that the magnetic insulating means interrupts the magnetic flow path between the non-resonant assembly and at least one of said parts defined by the piston (10) and the cylinder (2).
 3. The arrangement according to claim 2, in which the resonant assembly carries at least one spring means (8) mounted to the actuating means (3) and to the non-resonant assembly and which is resiliently and axially deformable in the displacement direction of the piston (10), characterized in that the magnetic insulating means interrupts the magnetic flow path between said spring means (8) and at least one of said parts defined by the piston (10) and the cylinder (2).
 4. The arrangement according to claim 2, characterized in that the magnetic insulating means interrupts the magnetic flow path at least between the actuating means (3) and the piston (10).
 5. The arrangement according to claim 4, characterized in that the magnetic insulating means is defined by at least part of the piston (10).
 6. The arrangement according to claim 5, characterized in that the magnetic insulating means is defined by at least part of the cylinder (2).
 7. The arrangement according to claim 4, characterized in that the magnetic insulating means comprises at least one element made of a non-magnetic material disposed between the piston (10) and the actuating means (3).
 8. The arrangement according to claim 7, characterized in that each element in a non-magnetic material is defined by a coupling portion (12) of the piston (10) connecting the actuating means (3) to a top portion (11) of the piston (10).
 9. The arrangement according to claim 4, characterized in that each element in a non-magnetic material is a pastille (40) defined adjacent to the actuating means (3) and attachable to a respective part defined by the piston (10) and by the cylinder (2).
 10. The arrangement according to claim 1, characterized in that the magnetic insulating means is a lining provided in the part to which it is affixed.
 11. The arrangement according to claim 5, characterized in that the piston (10) is massive.
 12. The arrangement according to claim 8, characterized in that the coupling portion (12) has an end mounted to the inside of the top portion (11) of the piston (10).
 13. The arrangement according to claim 12, characterized in that the top portion (11) is tubular and the coupling portion (12) is an insert mounted to the inside of the top portion (11).
 14. The arrangement according to claim 13, characterized in that the insert is mounted to the top portion (11) by any one of the processes, such as interference, welding, or gluing.
 15. The arrangement according to claim 7, characterized in that the element in a non-magnetic material presents a thickness of at least about 10 mm. 